Mausoleum
of Hadrian

"He was buried near the river itself, close to the Aelian
bridge; for it was there that he had prepared his tomb, since
the tomb of Augustus was full, and from this time no body was
deposited in it."

Cassius Dio, Roman History (LXIX.23.1)

Until the time of Nerva, the ashes of the Roman emperors had
been placed in the Mausoleum of Augustus, although Trajan's remains
were put in the base of his column in the Forum of Trajan. Hadrian
built a new mausoleum (Mausoleum Hadriani), which was completed
by his adoptive son and successor Antoninus Pius in AD 139, the
year after Hadrian's death. (The largest tomb in the Roman world
was that of Augustus, which Hadrian consciously did not attempt
to surpass.) In it were placed the cinerary urns of Hadrian;
Antoninus Pius and his wife, Faustina; Lucius Verus; Marcus Aurelius
and his son, Commodus; Septimius Severus and his family, Julia
Domna, Geta, and Caracalla. And there they remained until the
sack of Rome by Alaric and the Visigoths in AD 410. When Aurelian
began to surround the city with a new wall(Muri Aureliani)
in AD 271, the mausoleum was incorporated as part of the defense
and turned into a fortress. (The Pons Aelius that approaches
the tomb was built by Hadrian in AD 134, three of its central
arches still standing.)